FIG. 5 shows a construction of a prior art semiconductor laser device using a two beam array semiconductor laser diode element. In FIG. 5, reference numeral 1 designates a two beam array semiconductor laser diode (hereinafter referred to as two beam array LD) having a pair of light emission regions. Reference numeral 2 designates a submount for mounting of the two beam array LD element 1. Reference numeral 3 designates a photodetector for detecting the light beams which are emitted from the rear facet of the two beam array LD element 1. Reference numeral 4 designates a stem for fixing the submount 2 and the photodetector 3. Reference characters A and B designate light beams which are emitted from the front facet of the two beam array LD element 1. Reference characters A' and B' designate light beams which are emitted from the rear facet of the two beam array LD element 1. These light beams A' and B' are emitted from the same cavity as light beam A and B.
The device will operate as follows.
When sufficient current flows in the two beam array LD element 1, light beams A and B are emitted from the front facet of the element and the light beams A' and B' are emitted from the rear facet thereof. Since the light beams A and A', and the light beams B and B' are emitted from the same cavity, respectively, the light intensities of the light beams A and A' and those of the light beams B and B' are in proportional relationship. Accordingly, the light intensities of the light beams A and B can be monitored by detecting the light intensities of the light beam A' and B', respectively, with the photodetector 3, which are emitted from the rear facet of the two beam array LD element 1.
Since there may be cases where the two beam array LD device should be used with making the two light emission portions emitting independently, the two beam array LD element 1 and the submount 2 are provided with a separation groove for electrically separating the two light emission portions. Further, the interval between the two light emission portions is set at about 100 to 200 microns.
The prior art semiconductor laser device is constructed in such a manner, and the two light beams A' and B' emitted from the rear facet of the two beam array LD element 1 have beams with angles of about 10.degree. to 15.degree. in the direction of straight line connecting the two light emission points whereby the light beams A' and B' are overlapped on the photodetector 3. Accordingly, although the two light emission portions are capable of independent light emission, it is impossible to independently monitor the light intensities of the light beams A' and B' with the photodetector 3. The photodetector is stereoscopically constructed using a stem to receive laser light beams sufficiently broadened in the longitudinal direction to enhance the detection efficiency of the photodetector. However, the above-described construction requires bonding of the laser element and the photodetector at 90.degree. relative to each other, thereby complicating the fabrication process.